Since their introduction in the late 1980s, proton pump inhibitors have improved the treatment of various acid-related gastrointestinal (GI) disorders, including gastroesophageal reflux disease (GERD), peptic ulcer disease, Zollinger-Ellison Syndrome (ZES), ulcers, and nonsteroidal anti-inflammatory drug (NSAID)-induced gastropathy. GERD encompasses three disease categories: non-erosive reflux disease (NERD), erosive esophagitis, and Barrett's esophagus. ZES is caused by a gastrin-secreting tumor of the pancreas that stimulates the acid-secreting cells of the stomach to maximal activity. Proton pump inhibitors have also be used to treat ulcers such as duodenal, gastric, and NSAID-associated gastric/duodenal ulcers.
As antisecretory drugs, proton pump inhibitors are currently the recommended first line therapy, being viewed as more effective than other treatments. In general, proton pump inhibitors offer superior gastric acid suppression over histamine H2-receptor blockers. The use of proton pump inhibitors by patients who suffer from gastric acid-related disorders is generally believed to have led to an increase in their quality of life, productivity, and overall well being.
Proton pump inhibitors are also used to treat extra-esophageal manifestations of GERD (asthma, hoarseness, chronic cough, non-cardiac chest pain), and with antibiotics for Helicobacter pylori eradication. The goals of GERD management are threefold: prompt and sustained symptom control, healing of the injured esophageal mucosa and prevention of GERD-related complications (including stricture formation, Barrett's esophagus, and/or adenocarcinoma). Pharmacological therapy with proton pump inhibitors forms the basis of both acute and long-term management of GERD. Proton pump inhibitors provide effective relief of symptoms and healing of the esophagitis, as well as sustaining long-term remission.
Although therapeutic efficacy is the primary concern for a therapeutic agent, the solid-state form, as well as the salt form of a drug candidate, can be important to its development. Each solid state form (crystalline or amorphous) of a drug candidate can have different physical and chemical properties, for example, solubility, stability, or the ability to be reproduced. These properties can impact the ultimate pharmaceutical dosage form, the optimization of manufacturing processes, and absorption in the body. Moreover, finding the most adequate form for further drug development, can reduce the term and the cost of that development.
Obtaining substantially pure crystalline, amorphous or even other non-crystalline forms is extremely useful in drug development. It permits better characterization of the drug candidate's chemical and physical properties and thereby allows identification of the form or forms with the desired combination of therapeutic effect and comparative ease of manufacture. The solid state crystalline form may possess more favorable pharmacology than the amorphous form or may be easier to process. It may also possess more storage stability.
The solid state physical properties of a drug candidate may also influence its selection as a pharmaceutical active ingredient and the choice of form for its pharmaceutical composition. One such physical property, for example, is the flowability of the solid, before and after milling. Flowability affects the ease with which the material is handled during processing into a pharmaceutical composition. When particles of the powdered compound do not flow past each other easily, a formulation specialist must take that fact into account in developing a tablet or capsule formulation, which may necessitate the use of glidants such as colloidal silicon dioxide, talc, starch or tribasic calcium phosphate. Another important solid state property of a pharmaceutical compound is its dissolution rate in aqueous fluid. The rate of dissolution of an active ingredient in a patient's gastrointestinal fluid may have therapeutic consequences since it impacts the rate at which an orally-administered active ingredient may reach the patient's bloodstream.
In chemical syntheses of drug candidates, such as ilaprazole, intermediates are prepared and unwanted by-products or impurities can be carried forward from earlier steps. Often filtration, separation, and/or purification steps are introduced to remove unwanted by-products or impurities. Incorporating such steps cannot only increase costs but can decrease the overall yield of the synthesis. Having a crystalline intermediate or a crystalline solvated form of the drug candidate within a multi-step synthesis can address these problems. A crystalline intermediate or a crystalline solvate of a drug candidate provides certain advantages—a high purity intermediate can reduce the need for other purification steps and reduce the cost of the synthetic process. Such crystalline compounds provide a focal point in the synthesis where the desired purity can be achieved before conversion to the actual drug product.
These practical physical properties are influenced by the properties of the particular solid state form of the compound, for example, by the conformation and orientation of molecules in the unit cell of the crystalline compound. A crystalline form often has different thermal behavior characteristics from an amorphous, a non-crystalline form or another polymorphic form. Thermal behavior is measured in the laboratory by such techniques as capillary melting point, thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) and may be used, for example, to distinguish some polymorphic forms from others. A particular solid state form generally possesses distinct crystallographic and spectroscopic properties detectable by powder X-ray diffraction (XRPD), single crystal X-ray crystallography, and infrared spectrometry among other techniques.